A 24-year-old man runs a marathon on an unusually hot and muggy day. Several hours later he becomes ill with fever, weakness, and painful swollen legs and passes dark brown urine. Which of the following is a common finding with this disorder?
- Urine orthotoluidine (Hematest) reaction will be negative.
- Serum will be pink.
- Serum creatine phosphokinase levels will be elevated.
- Serum haptoglobin levels will be elevated.
- Serum potassium levels will be lowered.
Answer(s): C
Explanation:
The clinical features of the patient described in the question are characteristic of rhabdomyolysis with myoglobinuria. Skeletal muscle injury releases large amounts of myoglobin into the circulation, and myoglobinuria produces a positive orthotoluidine reaction. Because myoglobin is quickly cleared from serum by the kidneys, the serum does not turn pink, as it does with hemoglobinemia. Muscle damage leads to elevated creatine phosphokinase levels and hyperkalemia. Myoglobin does not bind to haptoglobin as does hemoglobin, so serum haptoglobin levels are normal. The major complication of rhabdomyolysis is acute renal failure.
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